I'm not sure if this is a bug, an oversight or some weird attempt at marketing but I've managed to pick up an item for a Clockwork City quest without owning the DLC and without an active subscription. (I did visit the Clockwork City during a previous free ESO+ trial weekend, but not on this character and only picked up 1 daily quest, which I completed.)
I was exploring the Aldunz delve in Alik'r and picked up the Construct's Chestplate. I wasn't sure what it was (the info box said 'museum piece' but that didn't mean much) so I googled it and found out it's one of the items required for the quest/achievement The Precursor in The Clockwork City. Which is kind of frustrating because I had decided not to buy the DLC yet, until I've finished some of the other stuff I have to do in the game. So now I'm going to have to carry this around with me indefinitely, because I'm not sure I'd be able to get another if I destroyed it.
It would be better IMO if items like this worked like the Thieves Troves - everyone can see them but if you don't have the DLC or an active subscription you get a message saying you cannot interact with it.
PC EU player | She/her/hers | PAWS (Positively Against Wrip-off Stuff) - Say No to Crown Crates!
"Remember in this game we call life that no one said it's fair"